Science of the “Color Changing Markers”

Alright, admit it, you kind of wanted to be as cool as this little girl when you played with markers as a kid. But this product is actually pretty recent so unless you still play with markers, it’s pretty unlikely you’ve ever had such an opportunity. So what markers did we play with as kids? Chances are at some point, as a parent or kid, you came across the “magic” color changing marker commercials all over the TV, and eventually curiosity won out and you bought a pack. But how did they work? Only 10 years after their discontinued production, we’re here to find out.

 

Crayola Color Switcher Markers, the closest thing available today that compares to those old Crayola Color Changeable Markers, gives you the “magical” ability to draw on paper with a red marker and (after applying the “magic marker tip”) end up with a gold line! But the fun doesn’t stop there! This special pack of markers can go from black to orange, purple to coral, blue to aqua, and much, much more! So how is it possible that the ink from these markers changes color? The answer is in the pH.
Where did markers come from?

But markers weren’t always this advanced! The original “felt tip pen” was invented by a man namedSidney Rosenthal in 1953. Yet, no one could have predicted that the simple action of placing a felt tip on the end of a small ink bottle would lead to one of the most popular franchises and products in the history of modern civilization.

The Crayola brand was first invented by the color company known as Binney and Smith in 1864. Moving their way successfully through chalk, crayons, and pencils; the first pack of Crayola Markers was sold in 1978. And 10 years later, the first Magic Marker or color changing marker set was produced. Essentially, these packs include about 6 colored marker colors, and each marker contains an attached Color Change Tip, which can be used to draw over the other colors and “magically” change the pigment on the paper.

How does it work?

Although well known as a fun and creative kids toy, the chemistry behind the Crayola Color Changing Magic Marker, and other markers like it, actually involves a good deal of chemistry.

Provided here is a video in which the composition of the color changing markers as well as the markers they change is investigated.

As shown in this Crayola commercial, the color changing markers react with some of the pigments and not with others, therefore appearing to “take away” certain layers of the color while leaving others. This makes is seem as though the color is actually changing when in fact only a fraction of the pigment is being removed. In this blog post, we will explain why a combination of a strong base and acid will cause these colors to react.

So what’s the science behind it?

The actual ink in the Color Change Markers is an aqueous solution of a highly polar glycol (to keep the marker from drying out), a non-sudsing detergent (as a wetting agent), and some form of citric acid (to create an acidic pH).

This diagram represents the structure of citric acid. Note the large amount of OH bonds which make this molecule extremely polar – this will be mentioned later.

However the dyes in markers are not made up of only one dye, but a combination of many. For example, orange is a combination of red and yellow, purple is a combination or blue and red, and even red is a combination of different shades of fuchsia and yellow, as shown below. As mentioned before in the video, by “hiding” certain pigments within the marker color, something that draws on red may end up a bright shade of gold after undergoing the chemical reaction.

Most of these marker dyes have a pH somewhere between 1-7 due to the concentration of citric acid, and will thus react with strong bases. Crayola uses acid-base reactions like this to produce the “magic” we see.

The “Color Change Tips”, as they are called called, contain an aqueous solution consisting of a highly polar glycol, a non-subsidizing detergent similar in composition to what is in the marker itself. In addition to the acid-base reaction, (as shown above), it is speculated that because “like dissolves like”, the polar glycol and polar citric acid may partially dissolve each other. This could cause the appearance of certain colors disappearing.

The Color Change Tip also has a strong basic pH that reacts with the other pigments in the ink. It is speculated that the Color Change Tip mostly composed of a dilute solution of NaOH, because it reads at apH above 10. When this “invisible ink” is spread onto dye from the regular markers, an acid base reactiontakes place.

Acid base reactions commonly produce a conjugate acid and conjugate base as shown in the diagram above. Citric Acid, a common component of marker dye, is an weak organic acid. With the addition of a strong base, such as NaOH from the special marker tip, a reaction similar to the one shown above is assumed to happen.

Unfortunately, due to trade secrets and copy writes of Crayola, the true chemical reactions remain unknown. However there is still strong speculation that the aforementioned chemicals are the main factors in the product. And if you’re still interested, feel free to try it for yourself!

How does this apply to me?

Acid-base reactions are everywhere! One of the most important examples is plant growth. Plant growthsometimes depends on the pH of the surrounding soil.   For example, blueberry plants require highly acidic soil. However, highly acidic soil usually lacks certain minerals such as Calcium, and Phosphorus, making it unsuitable for other plants such as Evergreens. Creating more alkaline or acidic compositions in soil falls largely into a branch of chemistry dealing with neutralization reactions of soil.  Without this study and these careful measurements, those locally grown fresh blueberries you love might not have been possible.

Another interesting acid and base reaction is the delicious food: Sherbet! It isn’t that noticeable when eating,but once the sherbet is put in your mouth a reaction occurs. There is a sweet powder in sherbet that reacts with the saliva in your mouth producing carbon dioxide. The acids in the powder usually include citric, malic or tartaric acid, depending on the brand. The bases are sodium bicarbonate, sodium carbonate or magnesium carbonate. With the addition of water in saliva, these chemicals complete an acid-base reaction that leads to the unique taste of sherbet’s tart but sweet flavor.

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